PROJECT SUMMARY Bioelectric mechanisms are emerging to be novel regulators of organ specification, growth and patterning during normal as well as regenerative development of organisms. Bioelectric properties of cells are determined by membrane localized channels that regulate entry of charged ions. Our interest in this topic stems from original findings that indicate membrane potentials of cells in gastrula stage zebrafish embryos appear to be in different states over distinct regions of the embryo. We are interested in understanding how these distinct bioelectric states may be generated and what is their significance. Gastrulation is a complex developmental stage when the dorsal-ventral and animal-vegetal axes are specified and cells begin to acquire specific fates. During this stage diverse morphogens and their effectors interact with each other to restrict their zones of influence and induce cell differentiation. We have determined that phenotypes induced by chemical inhibition of FGF by SU 5402 could be rescued by global increase in membrane depolarization across the embryo. We hypothesize that modulation of membrane potential could be altering the threshold for the specific inhibited FGF effector. To dissect this our project aims to define whether there is any specific membrane channel that is regulating a FGF effector or conversely and whether there is a membrane channel being regulated by FGF. To achieve our desired aims in a systematic manner, we first propose to characterize the pattern of voltage membrane potentials across the zebrafish gastrula over time with voltage sensitive dyes and the use of genetically encoded voltage indicators. We then plan to define the specific ion transporters mediating these bioelectric patterns as well as determine if they can influence the expression of core morphogenetic pathways during axis determination. Lastly, we will interrogate the interactions that bioelectric signaling has with Fgf signaling during axis determination and elongation. Most importantly, this study will be primarily accomplished with the support of undergraduate researchers who are all women and 50% of who first generation or researchers of color.